This invention relates to a method for manufacturing gallium phosphide by reducing gallium orthophosphate (GaPO.sub.4) in a reducing atmosphere while heating it.
A GaP single crystal is widely used as a material for electroluminescence as well as for photocells, light emitting diodes etc. A variety of methods are conventionally known for manufacturing gallium phosphide which is used as a material for the GaP single crystal. A method for reducing gallium orthophosphate in a reducing atmosphere has recently been adopted due to freedom from hazard and since it involves a low manufacturing cost. This method comprises the steps of charging gallium orthophosphate in a reactor and introducing a hydrogen gas as a reducing agent into the reactor to cause gallium orthophosphate to be reduced to gallium phosphide. This process is considered to proceed as follows: EQU 2GaPO.sub.4 + 7H.sub.2 .fwdarw. Ga.sub.2 O+ 7H.sub.2 0+ P.sub.2 (or 1/2P.sub.4) (1) EQU ga.sub.2 O.sub. H.sub.2 + P.sub.2 (or 1/2P.sub.4).fwdarw. 2GaP+ H.sub.2 O (2)
from these, it will be understood that gallium phosphide is formed by the reaction of phosphorus (P.sub.2 or 1/2P.sub.4) with gallium oxide (Ga.sub.2 O) and that gallium phosphide is not formed through liberation of oxygen direct from gallium orthophosphate. It is also surmised from the fact that gallium phosphide is formed in a needlelike crystal.
In the conventional method, however, intermediate product gallium oxide (Ga.sub.2 O) and phosphor (P.sub.2) are blown away during the reducing reaction with a poor yield and the manufacturing efficiency is lowered due to the slow reducing speed. When, for example, sufficient reduction is effected so as to obtain a material for a pn junction luminescence (light emitting diode), an actual yield of GaP is of the order of below 70% of the theory and a lengthy reduction time will be required.